Furnace-regulator system



Patented Mar. 27,1923.

UNITED STATES PATENT OFFICE.

ROBERT D. EVANS, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

FURNACE-REGULATOR SYSTEM.

Application filed ,0ctober 30, 1918. Serial No. 260,277.

To'aZZ whom it may concern:

Be it known that 1, ROBERT D. EVANS, a citizen of the-United States, anda resident of Wilkinsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Furnace-Regulator Systems, of which the following is a specification.

My invention relates to regulator systems and particularly to regulatorsystems for governing the operation of electric furnaces.

One object of my invention is to provide a regulator system of theabove-indicated character that shall control the operation of a furnacein an eflicient manner and be substantially free from hunting action.

Another object of my invention is to provide .a regulator system for anelectric furnace, having motor-operated electrodes, that shall governthe operation of the motors for raising and for lowering the electrodesin accordance with the current supplied to the furnace and be providedwith means for preventing hunting action thereby which isgoverned inaccordance with the operation of the motors.

In electric furnaces, it is very desirable that the movable electrodesbe automatically raised and lowered by motors, preferably electricmotors, in accordance with the current supplied to the furnace or by thearcs formed .by the respective electrodes. Moreover, it is customary toprovide electric furnaces of the above character with regulator systemsfor governing the operation of the motors which control the movements ofthe electrodes, and the regulator systems-are usually provided withanti-hunting devices for stabilizing the operation of the furnaces.

In an electric-furnace-regulator ,system' constructed according to myinvention, a motor is provided for raising and lowering each movableelectrode of th'e'furnace in aca prises two electromagnets which opposeeach other, one of the electrom'a ets being cordance with the currentflowing through such electrode. Eachregu'lator mm coine'nergized inaccordance with-'t 'e current flowing through the electrode associated;with thel regulator for governing :the'operationof two; switches which"controith'e op;

through the motor whenever the regulator,

is in a normal position.

The single figure of the accompanying drawing is a diagrammatic view ofa furnace-regulator system embodying my invention."

Referring to the drawing, an electric furnace 1, embodying two movableelectrodes 2 and 3, and a receptacle 4, containing abath of material 5,is c'onnectedto a threephase supply circuit comprising conductors 6, 7and 8. The'supply conductors 7 and 8 are respectively connected to theelectrodes 2 and 3, and the supply conductor 6 is connected to the bathof material 5.

Two motors 9 and 10, respectively com prising armatures 11 and 12, andfield windings 13 and 14, are provided for raising and lowering theelectrodes 2 and 3 by any suitable means, such, for example, as drums 15and 16, which are mounted upon the shafts of the armatures l1 and 12,and flexible connecting means 17 and 18 which are connected to theelectrodes 2 and 3 and are adapted to be wound upon the drums 15 and 16.

The motor 10, which governs the operation of the electrode 3, iscontrolled by means of a regulator 20, in accordance with the currentsupplied to the electrode 3, a'nd the motor 9, which operates the,electrode 2, is governed by a regulator'2l,'in accordance with thecurrent that is supplied to. the furnace throughthe electrode 2 {Theregulae tor 20. embodies amain control electromagneti22 havi'nga=winding.23, which is connected-to the supplyconductorB by means of=acurrent transformer 24:, an adjustable resistorj25 being connectedacross the windating' the speed of operation of :the' main controlgelectromagnet 22. The;

in 23 for regu main. control -electromagnet. 22.; further em-i bodies acore member 26 which is pivotally connected to a contact arm 27 and ismaintained in a retracted position by means of a spring 28. The contactarm 27 is provided with a contact member 30 which is selectively movedinto engagement with contact fingers 31 and 32, according to theenergization of the main control electromagnet 22. An auxiliarypolarized magnet 33, having a winding 34 and a core 35, is connected tothe contact arm 27 and is adapted to oppose the action of the maincontrol magnet 22, under predetermined condltions, for preventino ahunting action by the regulator. The winding 34 of the auxiliaryelectromagnet is connected across the armature 12 of the motor 10 and isshunted by means of an adjustable resistor 36 for adjusting the speed ofits operation.

Two electromagnetic switches 37: and 38, which are selectively operatedby means of the main control magnet 22, are provided for determining thedirection of rotation of the motor 10 and, consequently, the position ofthe electrode 3 relative to the bath of material 5. The switch 38embodies a winding 39, which is connected across an auxiliary supplycircuit,comprising conductors 40 and 41, whenever the contact members 30and 31 are in engagement with each other, and three switch members 42,43 and 44. The two switch members 42 and 43 serve for connecting thearmature 12 of the motor 10 through a resistor 45, across the supplyconductors 40 and 41, in order to effect rotation of the motor 10 in acounter-clockwise direction and thus raise the electrode 3.

The switch 37 embodies a winding 46, which is connected across thesupply conductors 40 and 41 when the contact terminals 30 and 32 are inengagement with each other, and three switch members 47, 48 and 49. Thetwo switch members 47 and 48 serve for connecting the armature 12 of themotor 10 across the supply conductors 40 or 41 in a manner to effectrotation of the motor 10 in a clockwise direction and thus permit thelowering of the electrode 3. The switch members 49 and 44 of theswitches 37 and 38 serve for completing a dynamic braking circuitthroughthe armature 12 whenever the two switches are in released positions. Thefield winding 14 of the motor 10 is connected across the supplyconductors 40 and 41, through an adjustable resistor 50.

The regulator 21, which governs the operation of the motor 9 inaccordance with the current supplied to the electrode 2, em-

4 bodies a mam-control or contact-making ammeter 52 having an energizingwinding 53 and a core member 54, which is pivotally connected to acontact arm 55. The core member 54is retracted by means of a spring 56.-and the energizing winding 53 is connected tothe supply conductor 7 bymeans of a current transformer 57. An adjustable resistor 58 is providedfor governing the sensitiveness of the magnet. The contact arm 55 isprovided with a contact terminal 60 which selectively engages thecontact fingers 61 and 62 according to the energization of the magnet52. L

An auxiliary polarized magnet 63, comprising a winding 64 and a coremember 65, which is pivotally connected to the contact arm is providedfor opposing the action of the electromagnet 52 under predeterminedconditions so as to prevent a hunting action by the regulator 21. Thewinding 64 is connected directly across the armature 11 of the motor 9in order to be energized in accordance with the counter-electromotiveforce (of the motor, and an adjustable resistor 66 is connected acrossthe winding 64 for gover ing the sensitiveness of the auxiliary magnet.

Two switches 69 and 70 are selectively controlled by the main-controlelectromagnet 52 for governing the direction of rotation of the motor 9and,accordingly, the position of the electrode 2. The switch 70 embodiesa winding 71, which is connected across the supply conductors 40 and 41whenever the contact members 60 and 61 are in engagement with eachother, and three contact members 72, 73 and 74. The two contact members72 and 73 serve to connect the armature 11 through a resistor 75 acrossthe I supply conductors 40 and 41 whenever the switch 70 is in anoperative position. The motor 9 is rotated in a counter-clockwisedirection when connected to the supply con-V ductors 40 and 41, throughthe switch members 7 2 and 7 3. in order to raise the electrode 2 fromthe bath of material 5. r

The switch 69 embodies a winding 76, which is connected across thesupply conductors 40 and 41 when the contact members 60 and 62 are -inengagement with each other, and three switch members 77, 78 and 79. Thetwo switch members 77 and 78 serve for connecting the armature 11 of themotor 9 across the supply conductors 40 and 41 in a manner to effectclockwise rotation of the motor and thus permit a lowering of theelectrode 2. The switch members 79 and 74 of the switches 69 and 70serve for completing a dynamic-braking circuit through the armature 11whenever the switches are in a released position. The field winding 13of the motor 9 is connected across the supply conductors 40 and 41,through an adjustable resistor 80.

In order to explain the operation of the thebath of material 5 that thecurrent flowing through the conductor 8 is above normal value, theenergization of the winding 23 of the contact-making ammeter 22 willbeincreased in a manner to effect engagement between the 'contactmembers 31 and 30.

' Upon engagement of thecontact members 30 when thecounter-electromotive force of the armature 12 is raised to apredetermined point, the auxiliary magnet 33 will overcome the action ofthe contact-making ammeter 22 and de-energize the motor 10 by releasingthe switch 38. In this regard, it may be noted that the time at whichthe auxiliary electromagnet 33 overcomes the action of the magnet 22 maybe adjusted by means of the resistors 25 and 36 which are respectivelyassociated with the windings 23 and 34 of the two electromagnets. Theauxiliary magnet is adapted to stop the motor 10 at such point as toprevent over travel thereby and consequent hunting by the regulator 20.

In case the electrode 3 is raised above the bath of material 5 to suchposition that a current below normal value is flowing through the supplyconductor 8, the energization of the contact-making ammeter 22 isreduced to such point that engagement is effected between the contactmembers 30 and Upon engagement of the contact members 30 and 32, theswitch 37; is operated for connecting the armature 12 of the motor 10across the supply conductors 40 and 41. Thus the motor is operated in aclockwise permit the lowering of the electrode 3. Simultaneously withthe operation of the motor 10, the polarized auxiliary magnet 33 isenergized by the counter-ele'ctromotive force of the armature 12 toseparate the contact members 30 and 32.

It is deemed inadvisable to completely I trace the operation of theregulator 21 for governing the motor 9 to determine the'position of theelectrode 2, inasmuch as the regulator 21 operates in a manner-similarto the operation above set forth in'discussing the regulator 20. Fromthe above description, it will be notedthat the two electrodes 2 and 3are governed in accordance with the current which is supplied to them 1through the conductors 7 and. 8 and that a hunting action is preventedby the auxiliary polarized magnets 33 and 63, which-are governed inaccordance with the counter: electromotive' force of the motors?) andvl0.

. regulator.

netic device having two electromagnets for,

controlling the operation of the motor, one of said electromagnets"being energized in accordance with the current supplied to the furnaceand the second'electromagnet being energized in accordance with theelectrical conditions of the motor to prevent hunting .action by saiddevice.

2. In combination, an electric furnace, a

motor for adjustingan electrode of the furnace, a regulator comprisingmeans for operating' the motor in accordance with the current suppliedto the furnace and for completing a dynamic. braking circuit through themotor, and means controlled by the counter-electromotive force of themotor for preventing hunting action by the 3. In combination, anelectric furnace having an operating motor, and a regulator comprising amain electromagnet for operating the motor in accordance with thecurrent supplied to the furnace and means comprising an uxiliaryelectromagnet governed in accordance with the motor electricalconditions for opposing the action of the main electromagnet to preventhunting action b it.

4. he combination with a supply circuit, and an electric furnaceconnected to the supply circuit, of a motor for adjusting the furnace,an electromagnetoperated in accordance with the current supplied to thefurnace, two switches selectively operated by said electromagnet forgoverning the operation of the motor, and means controlled by the motorfor preventing hunting action by'the electromagnet.

5. The combination with a supply circuit,-an electric furnace connectedto the supply circuit, and a motor for varying the are obtained in thefurnace, of an electro- '6. .The combination with a supply circuit I andan electric furnace connected to the supply circuit, of a motor forraising and owering a furnace electrode, an electricregulator-comprising a main electromagnet for selectively effectingrotation of the motor in-accordancewith the current supplied to thefurnace, and means comprisingan I auxiliary magnet controlled by saidmotor I of said regulator to prevent hunting action.

8. Thecombination with a polyphase supply circuit, and an electricfurnace connected to the supply circuit, of motors for operating thefurnace electrodes, and regulators for severally operating said motorsin accordance with the current supplied to the furnace, and meanscontrolled by the counter-electromotive force of the motors formodifying the action of said regulators to prevent hunting action.

9. The combination with an electric fur- 'nace having a plurality ofelectrodes, and a polyphase supply circuit connected to the furnace,of,mo,tors for varying the position of the electrodes, regulator meansfor selectively operating the motors in a forward and in a reversedirection according to the current supplied to the furnace and forcompleting dynamic braking circuits through the motor, and meansgoverned by the counter-electromotive force of the motors for preventinghunting action by the regulator means.

- 10. In a regulator for an electric furnace having an electric motorfor adjusting the arc formed therein, an electromagnet operated inaccordance with the current supplied to the furnace, two'switchescontrolled by said electromagnet for operating the motor in a forwardand in a reverse direction and for completing a dynamic-braking cir- 1nI cult through the motor under certain conditions, and means controlledby the motor for preventing hunting action by said electromagnet.

11. In a regulator for an electric furnace having an electric motor foradjusting the are formed therein, electromagnetic means operated inaccordance with the current supplied to the furnace, two switchesselectively operated by said means for effecting operation of themotoreither in a forward or in a reverse direction, an electromagnet foropposing the action of said electromagnetic means, and means forenergizing said electromagnet in accordance with thecounterelectromagnetic force of the motor to prevent hunting action bythe electromagnetic means.

12. In a regulator for an electric furnace, the combination comprisingan electric motor and a main control element for governbraking circuitthr ugh the motor, and means for modifying the operatlon of theregulator in accordance with the electric conditions of the associatedmotor to prevent hunting action.

14. In combination, a plurality of energytranslating devices, means forseverally adjusting said devices in accordance with the amount ofcurrent being supplied thereto, and means controlled by an electricalcondition of said adjusting means for changing the action of saidadjusting means to prevent hunting action.

15. The combination with a supply circuit and a plurality ofenergy-translating devices connected thereto, of regulators comprisingmeans for severally adjusting said devices in accordance with thecurrent traversing said devices and means controlled by an electricalcondition of said adjusting means for changing the action of saidadiusting means to prevent hunting action.

16. The combination with a supply circuit and a plurality ofenergy-translating devices connected thereto, of means for adjustingsaid devices, regulating means for controlling said adjusting means inaccordance with the amount of current being supplied to said devices andmeans controlled by an electrical conditionwof said adjusting means forchanging the action of said regulating means to anticipateand preventhunt- 17. In combination, a supply circuit, a. plurality ofenergy-translating devices connected thereto, means for severallyadjusting said devices to maintain a predetermined value of currenttranslated, regulatingmeans for said adjusting means, and meanseffective during the operation of said adjusting means for changing theaction of said regulating means in proportion to the variation from saidpredetermined value.

18. In combination, a supply circuit, a plurality'of energy-translatingdevices connected thereto, means for severally adjusting said devices tomaintain a predetermined value of current translated, regulating meansfor said adjusting means, and means for causing said regulating means todemergize said adjusting means before said predetermined value of energyis reached, the difference between the value at which said adjustingmeans is de-energized and said termined value of current through saidfurnace and meansfor causing said regulator to de-energize said motorbefore sald predetermlned value is reached, the difference in value atwhich said motor is de-energized and said predetermined value beingproportional to the counter electromotive force of said motor.

20. The combination with a supply circuit and an electric furnaceconnected thereto, of a motor for raising and lowering a furnaceelectrode, an electric regulator comprising a main electromagnet forselectively effecting rotation of the motor to maintain a predeterminedvalue of current traversing said electrode and means comprising anauxiliary ma et controlled by said motor for so modifying the action ofthe main magnet as to cause it to effect de-energization of said motorbefore'said predetermined value of current through said electrode isreached.

21. The combination with a supply circuit and an electric furnaceconnected thereto, of a motor for raising and lowering a furnaceelectrode, an electric regulator comprising a main electromagnet forselectively effecting rotation of the motor to maintain a predeterminedvalue of current'traversing said electrode, and means comprising anauxiliary magnet controlled by said motor for so modifying the action ofthe main magnet as to cause it to effect de-energization of said motorbefore said predetermined value of current through said electrode isreached, the difference between the current value at which said motor isde-energized and said predetermined current value being directly inproportion to an electrical condition of said motor.

22. The combination with a supply circuit and an electric furnaceconnected thereto, of a motor for raising and lowering a furnaceelectrode, an electric regulator comprising a main electromagnet forselectively effecting rotation of the motor to maintain a predeterminedvalue of current traversing said electrode, and means comprising anauxiliary magnet controlled by said motor for so modifying the action ofthe .main magnet as to cause it to effect de-energization of said motorbefore said predetermined value of current through said electrode isreached, the diiference between the current value at which said motor isde-energized and said predetermined current val- :ie being directly inproportion to the counter electromotive force of said motor.

In testimony whereof, I have hereunto subscribed my name-this 18th dayof Oct. 1918.

ROBERT D. EVANS.

